The idea of lenses constituted of silicone hydrogel was first proposed over 20 years ago. The potential advantages have been clear but the technological challenge was as tough as needing to mix oil and water to provide an optically clear product. Researcher organizations must date invested considerable tutorial and monetary resources to realize the excessive efficiency tender lenses of today. They've executed this fairly simply because they see this material as the way ahead and the ultimate normal of the future.
On the time of writing, silicone hydrogel lenses can be found within the USA from four producers: "Night time & Day" and "O2OPTIX" from CIBA Imaginative and prescient, "Pure Imaginative and prescient" from Bausch & Lomb, and "Acuvue OASYS" and "Advance" from J&J Imaginative and prescient Care.
OXYGEN TRANSPORT
So what’s so particular about silicone hydrogel as a lens materials? Basically, the nice good thing about this material is it’s skill to transport oxygen to the eye and thus maintain proper eye health. Trendy contact lens technology is all to do with oxygen permability, which is measured using the "Dk" index. And for optimum oxygen transmission, this should be as excessive as possible.
The Dk of conventional, non-silicone based mostly hydrogel lenses is immediately associated to the quantity of water that the fabric can hold, since oxygen dissolves into the water-component of the fabric and thus diffuses via the lens. The Dk in actual fact will increase logarithmically with growing water content. Water itself has a Dk of only 80, thus putting a ceiling on the Dk of convential supplies, and the unique soft contact lens material, polyHEMA, possesses a Dk of solely round 10 (with a water content of about 38%).
Nevertheless, in silicone hydrogels, the relationship between Dk and water content material is the opposite. Here larger water content material implies decrease Dk. With these lenses Dk increases considerably as the silicone content - not water content - of the lens increases. The Dk values of silicone hydrogel contact lenses are much greater than these of older gentle lens materials.
SLEEPING IN CONTACT LENSES
In response to market knowledge from CIBA Imaginative and prescient, eighty four% of soft contact lens wearers often sleep with their lenses in, and one-third admit to doing this regularly. 25% of wearers of one to 2-week disposable lenses with low oxygen transmissibility often or routinely sleep in their lenses overnight. And 72% of sentimental contact lens wearers stated they would favor to be allowed to wear their lenses in a single day provided it was safe.
Thus the demand for lenses with the capablities of silicone hydrogels is evidently very high with nearly three-quarters of soppy lens wearers wanting to have the ability to sleep in their lenses.
LENS HANDLING
Silicone hydrogel lenses are considerably more rigid than their conventional counterparts, due to the presence of silicone. This increased rigidity does possess some benefits, making the lenses markedly simpler to deal with and thus the ideal alternative for wearers with a much less delicate touch. There is a draw back to this nonetheless in that the rigidity makes the lenses much less liable to adopting the form of the attention so readily, ensuing within the possibility for a few of reduced comfort.
REDUCED DEPOSITIONS
Traditionally, the deposition of proteins and lipids has been a problem with contact lenses. The amount of depositions is essentially linked to the duration of damage, the lens materials and the tear composition of every individual wearer. With traditional lenses, a frequent substitute schedule enormously reduces the buildup of dangerous deposits.
Silicone hydrogel contact lenses have been confirmed to supply major advantages within the discount of protein and lysozyme deposition. Indeed, mixed with the proper alternative schedule and applicable care system, problems associated with protein deposition have turn into almost a thing of the past.
DRY EYES
An issue often encountered by wearers of conventional smooth contact lenses is one of a sense of discomfort and "grittiness" within the eyes towards the end of the day. It has been reported that after one week carrying silicone hydrogel lenses, the quantity of normal mushy lens wearers in a particular examine group who previously suffered significantly from end-of-day dryness, was reduced dramatically to solely 13% of the sample.
LIFESTYLE BENEFITS
Silicone hydrogel contact lenses also present some advantages that standard lenses don't. Continuous put on contact lenses will be notably helpful to be used by members of certain professions, corresponding to medical employees, police, the armed forces and firefighters who ceaselessly work unpredictable and lengthy hours.
Furthermore, an rising numbers of contact lens wearers can now take pleasure in active outdoor lifestyles, enjoying pursuits equivalent to camping and climbing where it's typically troublesome to handle and disinfect the lenses with the appropriate level of hygiene.
THE FUTURE FOR CONTACT LENSES
There may be a lot evidence to counsel that, owing to their important advantages over standard comfortable lenses, silicone hydrogel lenses will in the end, and sooner slightly than later, displace other sorts of contact lens because the prefferred choice for both day by day and overnight put on for the majority of contact lens wearers. Silicone hydrogel lenses provide a a lot improved physical performance, excellent dealing with properties and higher comfort. They might be considered as the ideal lens for common purpose use that exists immediately and are more likely to become the brand new on a regular basis standard.
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